1. Field
Disclosed herein is an apparatus and a method for measuring blood pressure in terms of the pulse characteristics of a subject.
2. Description of the Related Art
Various types of blood pressure measuring apparatuses have been developed due to an increasing public interest in health. Blood pressure measuring methods include a Korotkoff-sounds method, an oscillometric method, a tonometric method, and the like. The Korotkoff-sounds method, which is a typical blood pressure measuring method, measures the systolic pressure at which a sound of the pulse of a living being is first heard and the diastolic pressure at which the sound of the pulse is barely audible during a decompression process where the blood flow is blocked by sufficiently compressing a body part through which arterial blood flows.
The oscillometric method and the tonometric method are used for digital blood pressure measuring apparatuses. The oscillometric method detects a sphygmus wave, which occurs in a decompression process after sufficiently compressing a body part through which arterial blood flows so as to block arterial blood flow in a manner that is similar to the Korotkoff-sounds method, or in a compression process in which the body part is compressed at a predetermined compression speed. A pressure at which the amplitude of the sphygmus wave is at a specific level may be measured as a systolic pressure or as a diastolic pressure. Alternatively, a pressure at which the amplitude of the sphygmus wave changes suddenly may be measured as a systolic pressure or as a diastolic pressure.
During the decompressing process after compressing the body part at a predetermined compression speed, a systolic pressure is measured prior to a point in time at which the amplitude of the sphygmus wave is at a maximum, and a diastolic pressure is measured after a point of time at which the amplitude of the sphygmus wave is at the maximum. On the other hand, during the compression process in which the body part is compressed at a predetermined compression speed, the systolic pressure is measured after the point of time at which the amplitude of the sphygmus wave is at the maximum, and the diastolic pressure is measured prior to the point of time at which the amplitude of the sphygmus wave is at the maximum. The tonometric method compresses a body part so that arterial blood flow is not completely blocked and continuously measures blood pressure by using the size and form of a sphygmus wave generated by compressing the body part.
In the oscillometric method, a compression speed or a decompression speed is approximately determined based on a person having a normal pulse. However, when blood pressure of a subject having a slower than normal pulse is measured using the oscillometric method, since the number of peaks of a sphygmus wave is insufficient to measure an accurate blood pressure, it is difficult to ensure the accuracy of the measured blood pressure. On the other hand, when blood pressure of a subject having a faster than normal pulse is measured using the oscillometric method, since there are too many sphygmus wave peaks, it takes a long time to measure blood pressure.